Damp Proofing Walls: A Complete Guide to Fixing and Preventing Moisture Damage

If you were fortunate enough not to have damp issues with your property, you probably heard about someone else who did.

It's something that happens frequently, but thankfully we have numerous techniques for dealing with it. And damp-proofing walls are a popular and reliable treatment for preventing moisture penetration.

Continue reading to learn about the main causes of damping, different types of damp-proofing, products used, and much more.

damp proofing walls property care

What Is Damp Proofing a Wall?

For any home that shows signs of damp-related problems, we need to protect its structure to prevent the issue from worsening. It is done using a specific treatment to damp-proof the walls.

There are multiple methods, and what all methods have in common is that they work to create a barrier that keeps moisture from penetrating the walls.

The Different Damp Proofing Treatments for Walls

You’ll find several effective damp-proofing methods available, each with its own set of materials and techniques. Choosing one of them is primarily determined by the nature and severity of the case.

Here are the six most widely-used treatments for walls, with most of them serving as different types of Damp Proof Courses (DPC):

1. Damp Proof Membrane (DPM)

The membrane damp-proofing method entails inserting a physical layer, typically made of high-density polyethylene, into the walls or flooring to prevent water from penetrating.

It's one of the most successful DPC treatments for stopping groundwater from rising and reaching the building's structures. Thus, it became a legal requirement in 1875 for all buildings in the UK to have a damp-proof membrane in the flooring.

2. Damp Proof Injection

Damp-proof injection, also known as chemical damp proofing, is a type of DPC used when a building's original DPC has been damaged or deteriorated. The process is straightforward and requires little effort.

We start by drilling 150mm horizontally spaced holes and then inserting damp-proofing material with an injection gun. After a while, the chemicals do their magic and spread horizontally to form a water-repellent layer in the masonry.

3. Electro-Osmosis Damp Proofing

In some cases, the electro-osmosis technique is the only DPC that safely treats rising damp. Some of these cases include working with rubble masonry and low-level timber floors.

We use several supplies during this treatment, but the star of the show is the copper-coated cathode. We bury it into the ground through the walls. Then, with the help of other components, it generates an osmotic flow, which repels moisture from moving upwards.

4. Damp Proof Tanking

We mainly use a damp-proof tanking system on the interior walls of underground structures, such as cellars.

Tanking the walls refers to sealing them off from water infiltration. We do so by using either a waterproof tanking membrane, which is the same as a DPM, or a tanking slurry.

A tanking slurry is a thick cement-based coating that we apply to interior walls. This substance was scientifically formulated to penetrate the masonry and block off any passageways to prevent water from entering.

5. Cavity Wall Damp Proofing

Damp-related issues are uncommon in cavity walls due to their hollow design. However, in some situations, moisture does find its way into the internal wall. To address this, we use DPC injection, or other treatments, from both sides of a cavity wall.

It's critical to ensure that the cavity extends at least 225mm below the DPC; this plays a significant role in the treatment's effectiveness.

6. Replastering and Repainting

There are now plenty of damp-proof plaster and paint that are specifically designed to protect the interior walls from showing signs of damp. There are even spray versions of the damp-proof paint that makes application much easier.

Since we need to remove plaster or paint most of the time when applying a DPC, we always reapply them using the damp-proof types.

This makes them more of an integral part of damp proofing, but they should never be used on their own. You must first address the main cause of the damp. Otherwise, they'll be ineffective.

Walls That Require Damp Proofing

Damp-proofing walls are required to keep damp penetration at bay.

Our experts will decide where to apply the treatment based on a variety of factors, including the location of the structure and the seriousness of the damp problem. But, in general, these are the walls we usually work on:

External Walls

When dealing with moisture damage, one of our major concerns is the exterior walls. They're part of a structure that's directly exposed to extreme weather conditions.

When these walls are subjected to heavy rain, they can soak up water and cause damp issues, especially if they already have cracks.

Internal Walls

We also prefer treating internal walls as, in some cases, the exterior walls may have nothing to do with the damp on the inside. For example, roof damage or gutter leaks can easily cause moisture to seep through the internal walls, which is why it helps to have them protected.

Basement or Cellar Walls

Water damage and even flooding are things you hear a lot happening in basements and cellars. Because these structures are underground, they're more prone to developing cracks that allow rainwater in, hydrostatic pressure, and other problems, which is why damp-proofing is critical.

Solid Brick or Stone Walls

Having solid brick or stone walls with damp issues is more common than you think. There are several culprits to consider in such situations, but the most frequent are either damaged mortar lines or faulty construction.

Cavity Walls

Although one of the main characteristics of cavity walls is that they prevent water penetration, this isn't always the case.

For instance, if your home has poorly installed cavity wall insulation that leaves gaps unfilled, moisture may build up in those areas. Another example is when debris accumulates in the wall cavity, forming a bridge over which water can flow to the other side. 

Retaining Walls

If retaining walls aren't damp-proofed, moisture will infiltrate at some point. This is because this structure's sole purpose is to apply lateral pressure to the soil as the ground level changes.

It holds back moist soil for its entire lifetime, so naturally damp will gradually permeate the wall. It first manifests as regular damp signs like water stains, but if left untreated, it can advance to the wall collapsing.

Garage or Shed Walls

Both garages and sheds can have damp accumulation on their walls due to similar circumstances.

One of the popular contexts is reaching high humidity levels, which causes condensation. Water may also leak from surrounding pipework and seep through cracks in the walls.

Remember that if your garage is underground, it may face the same risks as basements and cellars.

Damp Proofing Products for Walls

The materials we use to damp-proof a structure vary greatly depending on the treatment we choose. However, there are three vital products used in different methods. And we’ll go over their functionality, pros, and cons.

Damp Proof Membrane

The membrane we use in DPM treatment is not just any layer; it meets multiple criteria established by British building standards. This polyethylene sheet, for example, should be at least 300μm thick and laid on specific material that won't contribute to its deterioration.

A damp-proofing membrane is a long-term solution for keeping damp from penetrating walls and flooring. However, using a low-quality membrane or incorrectly laying it can drastically reduce its effectiveness.

Damp Proof Cream

During the damp proof injection, we inject the chemicals that play a key role in this treatment into the walls. These chemicals usually take the form of silicone-based creams.

Damp-proofing creams have a distinct consistency that allows them to penetrate and stretch along the masonry, forming a strong barrier to stop water capillary rise.

They’re also great because we can apply them to a wall using hand pressure rather than high-pressure injection equipment.

This product doesn't have drawbacks; issues will only arise if it's improperly installed.

Damp Proof Paint

After addressing the underlying cause of the damp, we use damp-proof, also known as water-resistant paint, as the final product.

This paint has a thick consistency and is designed to act as a shield against moisture surfacing. It reduces the likelihood of wet stains appearing on the ceiling or walls, making it an excellent product for maintaining the aesthetics of your home.

In fact, you can easily seal small damp spoiled patches with the spray type of this paint. If there's anything negative to say about it, it's that it can't be used to treat damp on its own.

Main Causes of Damp on Walls

To properly deal with the damage caused by moisture penetration, we must first identify the source of the problem. There are three main causes of damp issues that we encounter:

  • Rising Damp: Groundwater can occasionally rise above its normal level and enter your home's structure through capillary action, which pushes water from the bottom to the pores of the masonry. This is known as rising damp, and it's usually caused by a deteriorated DPC.
  • Interstitial Condensation: The air in the house is generally carrying water vapour, and its ability to retain it decreases as it cools. When moist air penetrates through different parts of the house, it causes interstitial condensation. It progresses with poor ventilation, resulting in damp walls and steamy windows.
  • Penetrating Damp: When moisture begins to move from exterior walls to the interior, it's referred to as penetrating damp. It may happen due to something as simple as a heavy downpour or as complicated as a flaw in the building's construction.

How to Prevent Damp on Walls

Along with proper damp-proofing, there are a few things you can do to prevent moisture acclamation in walls:

  • Ensure proper ventilation by opening windows, especially in high-humidity areas like bathrooms.
  • Repair any leaks or water damage as soon as possible to prevent moisture buildup.
  • Apply waterproof paint to exterior and interior walls to limit water penetration.

How Do You Stop Rising Damp?

The quickest and most efficient way to block moisture from rising in your walls is to treat them with a damp-proof injection course. Not only will it stop and prevent rising damp, but it’ll also last for up to 30 years or even the lifetime of the building.

DIY vs Professional Services to Damp Proof Walls

Many people may believe that damp-proofing is a simple task, which it is, but only for experienced eyes.

DIY damp-proofing a wall poses numerous risks, not only to the interior of your home but also to the structural integrity of the property. Besides, if you don't pinpoint the root cause of the damp, your efforts will be futile.

When you hire a professional, they'll start by conducting a damp-proof survey to thoroughly examine the situation before getting to work. So along with maintaining the safety of your home, you ensure getting a reliable, long-term solution.

How Long Does It Take To Damp Proof a Wall?

Many factors influence the duration of damp-proofing, including the type of treatment, the size of the structure, and the severity of the damp. However, installation typically takes 3 to 5 days and sometimes a few weeks.

When Can You Replaster a Damp Proofed Wall?

You can start replastering the walls after 4 to 6 weeks. We usually try to postpone the replastering as much as possible to allow the wall to completely dry out and, in the case of an injection, the cream to fully settle in.

What Is the Cost of Damp Proofing Walls?

There's no set price for damp-proofing because multiple variables are considered, such as the damp-proofing method, materials used, and the number and size of the walls. But, we can say it starts at £300 and goes up to £5,000.

Wrapping Up

Damp-proofing your walls is a must if you want to spare yourself the stress and expense of dealing with moisture-related issues in the future. And when it comes to damp, the sooner the better is always the rule, as leaving it for an extended period can result in irreversible damage.

So if you’re in need of professional damp-proofing services, contact us now to have a damp-proof expert inspect your property and advise you on the best treatment for your walls!

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